JP6442144B2 - Radiation imaging apparatus, radiation imaging system, radiation imaging method and program - Google Patents

Description

  The present invention relates to a radiation imaging apparatus, a radiation imaging system, a radiation imaging method, and a program.

  A radiation generation apparatus that irradiates a subject with radiation, a radiation imaging apparatus that generates a clear radiation image by performing image processing on a radiation image obtained by digitizing a radiation image that is a radiation intensity distribution, and an image processing apparatus are used. Radiographic imaging systems have been commercialized. In such a radiographic imaging system, the radiation irradiating apparatus irradiates a subject with radiation, and the radiographic image data acquired by the radiation imaging apparatus is transferred to an image processing apparatus such as a control computer for image processing and storage. The image processing apparatus displays an image processed image on a display device such as a display.

  The radiation imaging apparatus uses a sensor array in which pixels composed of a conversion element that converts radiation into an image signal charge (electric signal) and a switch element such as a TFT that transfers the electric signal to the outside are arranged two-dimensionally. . By performing matrix driving using a switching element such as a TFT, the signal charge converted by the conversion element is read and transferred to the image processing apparatus, and an image is formed from the read charge amount.

  Each conversion element on the sensor array generates a signal directly or indirectly when irradiated with radiation. In a sensor that generates a signal indirectly, a conversion element of each pixel does not directly detect radiation, but detects visible light converted from radiation by a phosphor. In both direct and indirect sensors, each pixel generates and accumulates a certain amount of signal even when there is no radiation. This signal is referred to herein as dark charge.

  Dark charge has different characteristics in each pixel on the array, and when dark charge is superimposed on image signal charge (electrical signal) image signal charge due to radiation irradiation, image quality deteriorates by adding non-uniform offset to the image Let In order to prevent this, it is common practice to turn on the switch elements of each pixel periodically and / or immediately before radiation irradiation to discharge (reset) accumulated dark charges.

  When the dark charge is reset, if the image signal is superimposed on the image signal, it is not possible to separate them and extract only the dark charge. The resetting of the dark charge overlaps with the irradiation of the radiation, or if it is executed between the irradiation of the radiation and the reading of the image signal, the image signal is lost. For this reason, it is necessary to exclusively perform dark charge resetting and radiation irradiation, and a mechanism for synchronizing the radiation imaging apparatus and the radiation irradiation apparatus is provided for this purpose. A radiation imaging system having such a mechanism is described in Patent Document 1.

  When the irradiation of radiation on the pixels on the sensor array is started, electric charges are generated inside, the electric charges flow out to the bias lines connected to the respective pixels, and the current amount of the bias lines rapidly increases. For example, Patent Document 2 proposes a radiation imaging apparatus that detects the start of radiation and the like by detecting a change in the amount of current.

  Further, as described above, since dark charges are always generated on the sensor array, it is necessary to periodically perform a dark charge resetting operation. Therefore, as shown in FIG. 1, each row (L0 to L10...) On the sensor array is sequentially driven to turn on the switch elements, and reset scanning (TC101) is performed to reset the charge of each pixel connected to the target row. While changing, the change in the current amount of the bias line is detected. When the start of radiation is detected, the reset scanning is stopped at the line where the reset scanning was performed at that moment (TC102), and the switch element is turned OFF, so that the sensor driving state is an operation for accumulating image signal charges by radiation. A state is reached (TC103). In this state, radiation is detected by the sensor array.

  After the radiation irradiation is completed, each row on the sensor array is sequentially driven again to turn on the switch element, and the sensor driving state is set as the output operation state of the image signal charge, and the charge of the radiation image signal accumulated in each pixel is changed. A read operation is performed (TC104).

  At this time, each pixel in the row that has been reset at the time of detecting the start of radiation irradiation (TC102) has a part of useful image signal charges generated by radiation irradiation because the switch element is in the ON state. It will leak.

  Further, in the radiation irradiation apparatus, when the radiation irradiation is started, the radiation dose does not rise instantaneously, and if the rise of the dose is gradual, detection of the irradiation start by the radiation imaging apparatus may be delayed. In this case, a plurality of rows (L2 to L7 in the case of FIG. 1) from the actual start of irradiation to the row at the time when the radiation imaging apparatus detects the start of irradiation is reset and scanned. A part of useful image signal charges accumulated by radiation irradiation will flow out.

  As shown in FIG. 2, the pixel values of the rows (L2 to L7) from which useful charges have flowed out have less charge amount than the pixel values of the preceding and following rows (L0, L1, L8 to L10. Therefore, it is necessary to perform correction processing such as data interpolation. For example, Patent Document 3 is configured to wait for detection of the start of radiation irradiation while sequentially performing the reset scanning (TC301) for the rows that are not physically adjacent as shown in FIG. As a result, rows (L2, L4, L6, and L8) in which data at the time of radiation detection are missing are not continuously generated as shown in FIG. 4, and the missing row data is interpolated from the previous and next normal row data. Thus, a method for improving the accuracy of image data correction processing has been proposed. For example, when the missing row is L2, it has been proposed to perform interpolation processing using the preceding and following normal rows (L1, L3).

  In addition, in the radiation imaging system, it is required that the captured image can be displayed immediately after the imaging is performed in order to quickly determine whether the imaging has been normally performed (whether re-imaging is necessary). However, since the captured image requires various image correction processes such as an offset correction process for correcting the offset component of the image and a transfer time for transferring the image to the display device, a delay time from the imaging to the image display (display delay) Time).

  In order to reduce the display delay time, for example, Patent Document 4 discloses a method of transferring a preview image to a display device after performing offset correction.

JP 2003-33340 A JP 2009-219538 A JP2011-249891A JP 2012-152340 A

  In the case of a configuration in which the radiation imaging apparatus itself detects the radiation irradiation start as in Patent Document 2 and Patent Document 3, in the reset line when the radiation irradiation start is detected as described above, and in the vicinity of the line, Since the data at the time of radiation detection is lost, the image data is deteriorated. When displaying the preview image as a preview image, such as by reducing the acquired image, if the image degradation at the time of radiation detection is displayed, the operator cannot determine whether the image has been captured normally, There is a fear.

  For this reason, it is necessary to perform image correction processing to correct image data degradation. However, if image correction is performed on a preview image, a time loss for the correction processing occurs, and the image is displayed at high speed. There is a problem that can not be done.

  In order to solve such a problem, the present invention provides a radiation imaging technique capable of displaying an image without reducing an image display delay and without performing a process of correcting image degradation at the time of radiation detection.

A radiation imaging apparatus according to one aspect of the present invention includes a radiation detection array that is connected to a scanning line, and that includes a plurality of two-dimensionally arranged pixels that detect radiation and accumulate charges.
Reset control means for performing reset scanning for sequentially discharging charges accumulated in the pixels;
Irradiation detection means for detecting the start of irradiation of the radiation;
Imaging control means for controlling to obtain the image signal by stopping the reset scanning in response to detection of the start of irradiation of the radiation and reading out the electric charge accumulated in the pixels by the irradiation of the radiation;
Generating means for generating image data based on the image signal;
An output unit that outputs the image data to an external device,
A plurality of scan line groups consisting of non-adjacent scan lines are formed,
The reset control means sequentially selects scan lines forming one scan line group in one scan and scans a plurality of times so that scan lines included in all scan line groups are selected. Reset scan,
The generation means generates preview image data based on an image signal from a pixel connected to a scan line that forms a scan line group other than the scan line group including the scan line selected when the radiation is applied. Generated image data for main image including image data corrected based on an image signal from a pixel connected to a scanning line that was selected when radiation was applied is generated.

  According to the present invention, it is possible to display an image without reducing the display delay of the image and without performing a process of correcting the image deterioration at the time of radiation detection.

The timing chart which detects a radiation irradiation start and acquires a captured image. The figure explaining the image defect | deletion which generate | occur | produces by the delay of irradiation start detection. The figure explaining the imaging sequence by the conventional reset scanning. The figure explaining the image defect | deletion acquired by the conventional reset scanning. The figure which shows the structural example of the radiation imaging system concerning embodiment. The figure which shows the structural example of a radiation detection part. The figure explaining the imaging sequence in a radiation imaging system. The figure explaining the imaging sequence in a radiation imaging system. The figure explaining the thinning-out of the image for a preview. The figure explaining the image defect | deletion when irradiation start detection is the first line. The figure explaining the imaging sequence in 2nd Embodiment. The figure explaining the imaging sequence in 2nd Embodiment. The figure explaining the imaging sequence in 4th Embodiment. The figure explaining the imaging sequence in 5th Embodiment.

  Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the drawings. However, the constituent elements described in the embodiments are merely examples, and the technical scope of the present invention is determined by the claims, and is not limited by the following individual embodiments. .

(First embodiment)
FIG. 5 illustrates a configuration example of the radiation imaging system according to the embodiment of the present invention. The radiation imaging system includes a radiation imaging apparatus 1, a console 3 (information processing apparatus) that controls the radiation imaging apparatus 1, a display unit 4, and a radiation generation unit 500 that irradiates a subject with radiation. The radiation imaging apparatus 1 also includes a radiation detection unit 2 that detects radiation and generates image data, an irradiation detection unit 101 that detects the start and end of radiation irradiation, and an imaging control unit 102 that controls an imaging operation.

  The imaging control unit 102 includes a drive control unit 103 that controls scanning driving of the radiation detection unit 2, an image acquisition control unit 107 that performs acquisition control of image data from the radiation detection unit 2, an offset correction, a preview image generation, and the like. And an image processing unit 108 for performing the signal processing. The imaging control unit 102 also stores a storage unit 111 that stores an acquired image acquired from the radiation detection unit 2 and a communication control unit that controls data communication with the console 3 such as transferring the acquired image to an external console 3. 114. For data communication between the radiation imaging apparatus 1 and the console 3 by the communication control unit 114, for example, wireless LAN communication can be used. Note that data communication is not limited to wireless LAN communication, and may be wireless communication using another method or wired communication using a cable.

  The drive control unit 103 includes a reset scanning control unit 105 for performing a discharge (reset) operation of the accumulated dark charge at the radiation detection unit 2 periodically or at an arbitrary timing. In addition, the drive control unit 103 performs a read control unit 106 that performs drive control for reading an image from the radiation detection unit 2, and a line number that has been reset scanned at the time when radiation irradiation is started. The information storage part 104 at the time of irradiation detection for memorize | storing this information is provided.

  The console 3 includes a communication control unit 301 that controls data communication between the radiation imaging apparatus 1 and the console 3 such as receiving a captured image transferred from the radiation imaging apparatus 1. In addition, the console 3 includes a storage unit 302 that stores a received image transferred from the radiation imaging apparatus 1 and an image processing unit 303 that corrects the received image.

  The imaging control unit 102 reads, for example, a program stored in the storage unit 111 and performs overall control of the radiation imaging apparatus 1 based on the program. The radiation imaging apparatus 1 may be controlled by, for example, a control signal generation circuit (control circuit) such as an ASIC, or the overall control of the radiation imaging apparatus 1 is realized by both a program and a control circuit. May be.

  In the radiation detection unit 2, a plurality of conversion elements that convert radiation into charges are arranged along the scanning lines in the row direction, and the plurality of scanning lines are arranged in the column direction. For example, a switch element such as a TFT and a photoelectric conversion element (radiation detection element) are used as one pixel, and the pixels are arranged in a two-dimensional array. For example, a phosphor is provided on each pixel. In this case, the radiation incident on the radiation detection unit 2 is converted into visible light by the phosphor, and the converted visible light enters the photoelectric conversion element of each pixel. In each photoelectric conversion element, a charge corresponding to visible light is generated. Generated. In the present embodiment, the “conversion element” that converts the incident radiation by the above-described phosphor and photoelectric conversion element into electric charges will be described as a configuration example. However, the gist of the present invention is not limited to this configuration example. For example, it is also possible to use a so-called direct conversion type conversion element that converts incident radiation directly into charges without providing a phosphor. It is. The radiation detection unit 2 can acquire a radiation image by accumulating charges and reading charges by switching the TFT between ON and OFF.

  FIG. 6 is a diagram illustrating a configuration example of the radiation detection unit 2. Each pixel on the row on the two-dimensional sensor array of the radiation detector 2 is simultaneously addressed by the drive circuit 201, and the charge of each pixel on the row is held in the sample hold circuit 202. Thereafter, the charge (pixel output) of each pixel held by the sample hold circuit 202 is sequentially read out through the multiplexer 203, amplified by the amplifier 205, and then converted into digital image data by the A / D converter 206. Is done. Each time scanning of each row is completed, the drive circuit 201 drives each next row on the two-dimensional sensor array to sequentially scan, and finally, the charges of all pixel outputs are converted into digital values. Thereby, radiation image data can be read. At this time, scanning is performed while fixing the voltage applied to each column signal line connected to each pixel on the row to a specific value, and by reading out the acquired charge, dark charges are discharged and accumulated in each pixel. Dark charge is released (reset). The drive control unit 103 controls these detection units such as driving and reading operations.

  When the image data converted into a digital value by the A / D converter 206 is radiation image data obtained by radiation irradiation, the radiation image data is stored in the captured image memory 112 in FIG. Further, in the case of offset image data (offset data) acquired only from the dark charge component of each pixel without radiation irradiation, the offset image data (offset data) is stored in the offset image memory 113 in FIG.

  The offset correction unit 110 included in the image processing unit 108 can acquire a captured image from which unnecessary dark charge components are removed by performing offset correction by subtracting the component of the offset image data from the radiation image data.

  The irradiation detection unit 101 that detects the start and end of radiation irradiation can include an independent radiation detection sensor in addition to the radiation detection unit 2 that acquires an image. For example, by monitoring the amount of dark current discharged during the reset scan of the radiation detection unit 2, it is possible to detect the start / end of irradiation by the radiation detection unit 2 itself.

  The offset image data is acquired after, for example, radiation imaging, and the offset correction unit 110 performs offset correction. Note that the timing of acquiring the offset image data is not limited to after the radiation imaging. For example, offset image data may be acquired before radiation imaging, or one offset image prepared in advance may be repeatedly used for the offset correction process if there is little fluctuation in the dark charge component.

  The image processing unit 108 in the radiation imaging apparatus 1 includes a preview image generation unit 109 that generates a preview image by reducing the captured image from which unnecessary dark charge components are removed. For example, the preview image generation unit generates a preview image in advance of the captured image before offset correction after acquiring the radiation captured image. Then, the preview image generation unit 109 transfers the preview image generated in advance to the console 3 under the control of the communication control unit 114, thereby connecting the preview image generated in advance to the console 3. Can be displayed. Thereafter, the non-reduced captured image that has been offset-corrected by the offset correction unit 110 is transferred to the console 3 under the control of the communication control unit 114. A display unit 4 connected to the console 3 displays the transferred captured image as a main image.

  The communication control unit 301 of the console 3 controls data transmission / reception with the radiation imaging apparatus 1, and controls data transmission / reception with the imaging control unit 102 by operating software incorporated in a computer or the like, for example. Set parameters such as imaging conditions. The image processing unit 303 of the console 3 performs image processing for making the captured image received from the radiation imaging apparatus 1 into a form suitable for diagnosis. The storage unit 302 of the console 3 stores the captured image received from the radiation imaging apparatus 1. The display unit 4 displays a radiographic image based on the electric charges read from the radiation detection unit 2, an operation UI, and the like based on the captured image data transmitted to the console 3.

  FIG. 7 is a timing chart showing an imaging sequence in the radiation imaging system according to the present embodiment. FIG. 8 is a flowchart for explaining the flow of the imaging sequence of the radiation imaging system. The operation of the radiation imaging system will be described with reference to FIGS.

  When the radiation imaging apparatus is activated and enters an imaging standby state, the reset scanning control unit 105 of the drive control unit 103 periodically resets to prevent accumulation of dark charges in the two-dimensional sensor array constituting the radiation detection unit 2. Scanning is performed (TC 701 in FIG. 7 and S801 in FIG. 8). At this time, the reset scanning control unit 105 sequentially sets the scanning lines to be reset so that the conversion elements in rows (scanning lines) that are not physically adjacent on the two-dimensional sensor array are sequentially reset-scanned (TC701). The conversion elements of the selected scanning lines are sequentially driven. For example, in the first partial reset scan, the 2 × n-th row (incremented by 1 from n = 0) is sequentially selected and scanned (L0, L2, L4...), And in the second partial reset scan, 2 × The n + 1th row (incremented by 1 from n = 0) is sequentially selected and scanned (L1, L3, L5,...). Then, the first partial reset scanning and the second partial reset scanning are repeated, and the irradiation of radiation is awaited while discharging dark charges. Note that the selection order of the reset scan is exemplary, and the second partial reset scan may be performed first, and the first partial reset scan may be performed after the second partial reset scan.

  In the present embodiment, an example is shown in which scanning is performed by skipping rows one by one as non-adjacent rows (scanning lines), but the gist of the present invention is not limited to this example. For example, when scanning by skipping two rows in sequence as non-adjacent rows (scanning lines), the 3 × nth row is scanned in the first partial reset scan, and the 3 × n + 1th row is scanned in the second partial reset scan. The row is scanned, and the third partial reset scan scans the 3 × n + 2nd row.

  When scanning by skipping three rows in sequence, the 4 × nth row is scanned in the first partial reset scan, the 4 × n + 1th row is scanned in the second partial reset scan, and the third portion is scanned. In reset scanning, the 4 × n + 2nd row is scanned. In the fourth partial reset scan, the 4 × n + 3rd row is scanned. As described above, scanning may be performed by skipping arbitrary (m−1: m is an integer of 2 or more) rows, and the process up to the mth partial reset scanning may be repeated.

  If the rows are not adjacent, reset scanning may be performed by selecting a plurality of rows at a time. For example, in the case of scanning by skipping three rows at a time, the first partial reset scan and the third partial reset scan may be selected simultaneously to perform the reset scan. Alternatively, the second partial reset scan and the fourth partial reset scan may be simultaneously selected to perform the reset scan.

  In step S <b> 802, the irradiation detection unit 101 determines whether radiation irradiation has been started from the radiation generation unit 500. When the irradiation detection unit 101 does not detect the start of radiation irradiation (S802-No), reset scanning is repeatedly executed (S801).

  When radiation is emitted from the radiation generation unit 500 by a user operation input, the irradiation detection unit 101 detects this. When the irradiation detection unit 101 detects the start of radiation irradiation (S802-Yes), the reset scanning control unit 105 stops the reset scanning (TC702, S803). The readout scanning control unit 106 turns off all the TFT switches on the two-dimensional sensor array and puts all the pixels on the two-dimensional sensor array into a charge accumulation state (TC703, S804). When the reset scanning is stopped, the sensor drive state becomes the charge accumulation operation state.

  At this time, the drive control unit 103 stores the information of the two-dimensional sensor array when the reset scanning is stopped in the irradiation detection time information storage unit 104. That is, the drive control unit 103 stores information such as the line number when the reset scanning is stopped, the type of partial reset scanning when the reset scanning is stopped, the output value information when the irradiation is detected, and the like. To remember. In FIG. 7, the line number when the reset scanning is stopped is the eighth line (L8). Here, the type of partial reset scanning is, for example, a row that is not adjacent when performing reset scanning, such as scanning by skipping one row at a time, scanning by skipping by two rows, scanning by skipping by three rows, etc. ) To select information.

  In step S805, the irradiation detection unit 101 determines whether or not radiation irradiation has ended. If the irradiation of radiation has not ended (S805-No), the charge accumulation operation (TC703, S804) is continued.

  When the irradiation detection unit 101 detects the end of radiation irradiation (S805-Yes), the readout scanning control unit 106 turns on all the TFT switches on the two-dimensional sensor array, and all the pixels on the two-dimensional sensor array. To the charge output state. Then, in order to read out the electric charge accumulated by the radiation irradiation, the read scanning control unit 106 performs read scanning control (TC 704) for sequentially scanning the rows on the two-dimensional sensor array, and acquires radiation image data obtained by radiation imaging. (S806). The acquired radiographic image data is stored in the captured image memory 112.

  In the radiation image data, as described in the background art, the radiation image data of some rows may be deteriorated due to the detection delay between the actual radiation irradiation start and the irradiation start detection of the irradiation detection unit 101. . In order to reduce the influence of image data deterioration in the display of the preview image, the readout scanning control unit 106 acquires the information of the two-dimensional sensor array at the time of reset scanning stop stored in the irradiation detection time information storage unit 104. . Then, the readout scanning control unit 106 identifies image data in which a defect has occurred in the radiation image data.

  In FIG. 7, the irradiation detection unit 101 detects the start of radiation irradiation during the partial reset scanning of the 2 × n-th row. For this reason, as shown in FIG. 4, there is a defect in the radiation image data in the reset row (L8) when the reset scanning is stopped and the 2 × n-th rows (L2, L4, L6) before that. Become.

  Regarding the irradiation end timing of radiation, the irradiation detection unit 101 may detect the end, or the imaging control unit 102 may wait for a specific fixed time to end the irradiation and start the reading operation. good. When the end of irradiation is detected by the two-dimensional sensor array itself, for example, the row that has been reset scanned at the start of irradiation does not turn off the TFT switch, but continues to monitor the amount of current flowing through the bias line while keeping the TFT switch on. Thus, it is possible to detect the end of irradiation.

  Next, the preview image generating unit 109 of the image processing unit 108 determines image data used for generating a preview image. With respect to the image data of the row (2 × n + 1th row) selected by the second partial reset scan that has not been subjected to the reset scan at the start of radiation irradiation, there is no outflow of useful charges due to the reset, and thus image degradation is not caused. It has not occurred. The preview image generation unit 109 of the image processing unit 108 determines image data of a row other than the selected row in the partial reset scanning performed when the irradiation start is detected as image data used for generation of the preview image, and the preview image is determined from the image data. Is generated (TC705, S807). Then, the communication control unit 114 transfers the preview image generated by the preview image generation unit 109 to the console 3 before the main image for diagnosis (TC705, S807).

  Since the preview image transferred to the console 3 has no image deterioration at the time of irradiation detection, the image correction processing for deterioration is unnecessary, and can be immediately displayed on the display unit 4 (TC706, S808).

  Here, at the time of preview image generation by the preview image generation unit 109 of the image processing unit 108, from data other than the selected row in the partial reset scan at the time of irradiation detection (image data of the row (2 × n + 1)) Further, the preview image may be generated by thinning and reducing. When generating the thinned reduced image data, the preview image generating unit 109 may generate a reduced preview image obtained by reducing the captured image by thinning out pixels as shown in FIG. it can. In FIG. 9, for example, in the L1 row, hatched pixels 901 are used for generation (sampling) of a reduced preview image, and white pixels 902 to 905 are thinning targets.

  As shown in FIG. 9, by sampling from physically continuous pixels, the influence of specific frequency noise such as periodic signals (grid stripes) corresponding to the arrangement of the grid for removing scattered radiation in the subject is thinned out. Can be reduced. Note that the generation method of the reduced preview image by the preview image generation unit 109 is not limited to the example shown in FIG. 9, and another thinning method can be used. For example, for pixels used for generating a reduced preview image, a reduced preview image may be generated using interpolation processing. It is also possible to generate a reduced preview image by combining pixel values of pixels used for generating a reduced preview image and interpolation processing. Note that the thinning ratio is not limited to that illustrated in FIG. 9, and various ratios can be set.

  After the completion of the radiation image data readout operation (S806), the readout scanning control unit 106 turns off the TFT switches of all the pixels on the two-dimensional sensor array to enter the charge accumulation state (TC707, S809). The processing in this step is executed in parallel with the preview image generation and transfer processing (TC705, S807) and the preview image display processing (TC706, S808) described above. By performing parallel processing in this way, it is possible to shorten the time from generation and display of a preview image to generation and display of a main image for diagnosis described later.

  In step S810, the readout scanning control unit 106 determines whether the same waiting time as the accumulation time (TC703, S804) at the time of radiation irradiation has elapsed (elapsed waiting time). If this standby time has not elapsed (S810-No), the charge accumulation operation is continued. Thereby, accumulation of dark charge is continued. When the readout scanning control unit 106 determines that the same time as the accumulation time at the time of radiation irradiation has elapsed (S810-Yes), the readout scanning control unit 106 turns on all the TFT switches on the two-dimensional sensor array, All the pixels on the two-dimensional sensor array are set in a charge output state. Then, the readout scanning control unit 106 performs a readout operation and acquires offset image data of only the dark charge component (TC708, S811).

  Thereafter, the offset correction unit 110 performs offset correction using all of the radiation image data stored in the captured image memory 112 and the acquired offset image data (S812). The offset correction unit 110 acquires a captured image from which the dark charge component has been removed by offset correction that subtracts the component of the offset image data from the radiation image data.

  The communication control unit 114 transfers the captured image subjected to the offset correction by the offset correction unit 110 to the console 3 as a main image (TC709, S813).

  Unlike the preview image, the captured image is deteriorated in the data near the reset row at the time of irradiation detection, and this needs to be corrected. Therefore, the drive control unit 103 reads the information of the two-dimensional sensor array at the time of reset scanning stop (information at the time of irradiation detection) from the irradiation detection time information storage unit 104, and the communication control unit 114 is read by the drive control unit 103. Information at the time of irradiation detection is transferred to the console 3.

  The image processing unit 303 of the console 3 determines, from the information at the time of irradiation detection, the row number when the reset scanning is stopped, the type of partial reset scanning when it is stopped (non-adjacent row (scan line) selection method), Information on the output value when irradiation is detected is specified. The image processing unit 303 uses the specified information to perform image correction that interpolates the loss of the received captured image, and performs image processing suitable for various diagnoses (TC710, S814). The display unit 4 displays the captured image that has been subjected to image processing by the image processing unit 303 (TC711, S815: main image display).

  In the present embodiment, the image defect correction process at the time of irradiation detection is performed by the image processing unit 303 of the console 3. However, the present invention is not limited to this, and the image processing unit 108 in the radiation imaging apparatus 1 is not limited to this. May be implemented. In this case, there is no need to transfer information at the time of irradiation detection to the console 3, and the image processing unit 108 may perform correction processing using this information.

  When the reset line at the start of radiation irradiation detection is near the top of the line selected by the partial reset scan, image degradation due to the delay in the irradiation start detection is the one of the partial reset scan that was performed immediately before that. There may be a case where it also straddles the vicinity of the last line. As shown in FIG. 10, when the reset line at the time of irradiation start detection is the first line (L0) at the time of the first partial reset scan, the vicinity of the last line (L2) of the second partial reset scan performed before that. (N-2) +1, L2 (n-1) +1, L2n + 1)) may also occur. In this case, if no defect occurs, each pixel shows a pixel value 1001. When the first row (L0) at the time of the first partial reset scanning is a reset row at the time of irradiation start detection, the pixel value 1002 of the first row (L0) is greatly reduced with respect to the reference pixel value 1001. The pixel value 1003 of L2 (n−2) +1 row, the pixel value 1004 of L2 (n−1) +1, and the pixel value 1005 of L2n + 1 near the last row of the second partial reset scan are set to the reference pixel value 1001. On the other hand, it gradually decreases and approaches the pixel value 1002 of the first row (L0).

  However, even in this case, the preview image is generated from the image data of the row (2 × n + 1th row) selected by the second partial reset scan, which has not been reset at the time of irradiation detection. As shown in FIG. 2, the most noticeable image degradation is a row at the time of reset stop where the change in the pixel value in the column direction is the largest and a step is generated (for example, L7 in FIG. 2). In the case of FIG. 10, image degradation also occurs in the image data of the 2 × n + 1th row used as the preview image, but these do not appear as steps but appear as gentle gradations at the ends. The effect on the display of the preview image is negligible.

  In the radiation imaging apparatus according to the present embodiment, the radiation detection array 204 in which a plurality of pixels that accumulate radiation by detecting radiation is two-dimensionally arranged, and the charges accumulated in the pixels are sequentially emitted in units of lines. The radiation detection unit 2 includes a plurality of scanning lines.

  The reset scanning control unit 105 functioning as a reset control unit of the radiation imaging apparatus sequentially selects non-adjacent scanning lines to perform reset scanning. The irradiation detection unit 101 detects the start of radiation irradiation based on the charge released by the reset scanning.

  The imaging control unit 102 performs control to stop the reset scanning in response to the detection of the start of irradiation, and to read out the charges accumulated in the pixels of the radiation detection array 204 due to radiation irradiation and obtain an image signal.

  A preview image generation unit 109 functioning as a generation unit of the radiation imaging apparatus generates image data based on an image signal excluding an image signal from a scan line on which reset scanning is performed during radiation irradiation. Further, the communication control unit 114 functioning as an output unit of the radiation imaging apparatus outputs image data to an external apparatus.

  The imaging control unit 102 starts reading the electric charge for obtaining the image signal from the scanning line where the reset scanning is stopped.

  The reset scanning control unit 105 sequentially selects scanning lines according to a predetermined order, and the imaging control unit 102 reads out charges for obtaining an image signal starting from the scanning line where the reset scanning is stopped and reading according to the predetermined order. To do. The preview image generation unit 109 generates image data based on the image signal from the scanning line from which reading is started to the N / 2th scanning line, where N is the total number of lines from which image signals are obtained. To do.

  The communication control unit 114 outputs the image data generated by the preview image generation unit 109 and then outputs another image data including an image signal from the scanning line on which the reset scanning is performed during irradiation of radiation to an external device. Output to.

  The reset scanning control unit 105 divides the reset scanning into even lines and odd lines and performs them in a predetermined order. The preview image generation unit 109 generates image data based on the image signal of the odd line when the line where the reset scanning is stopped is an even line, and even when the line where the reset scan is stopped is an odd line Image data is generated based on the line image signal.

  In addition, the radiation imaging apparatus according to the present embodiment includes a radiation detection array 204 in which a plurality of pixels that detect radiation and accumulate charges are arranged two-dimensionally, and a plurality of elements for releasing the charges accumulated in the pixels. It is a radiation imaging device which has a radiation detection part provided with these scanning lines.

  The reset scanning control unit 105 that functions as a reset control unit of the radiation imaging apparatus performs reset scanning that sequentially releases charges accumulated in the pixels of the radiation detection array 204. The irradiation detection unit 101 detects the start of radiation irradiation based on the charge released by the reset scanning. The imaging control unit 102 performs control to stop the reset scanning in response to the detection of the start of irradiation, and to read out the charges accumulated in the pixels of the radiation detection array 204 due to radiation irradiation and obtain an image signal.

  A preview image generation unit 109 functioning as a generation unit of the radiation imaging apparatus generates image data based on an image signal excluding an image signal from a pixel that has undergone reset scanning during radiation irradiation. Further, the communication control unit 114 functioning as an output unit of the radiation imaging apparatus outputs image data to an external apparatus.

(Second Embodiment)
Next, a radiation imaging system according to the second embodiment of the present invention will be described. Since the configuration of the radiation imaging system in the present embodiment is the same as the configuration of the radiation imaging system in the first embodiment described above, description of each component will be omitted.

  11 and 12 are timing charts showing an imaging sequence in the radiation imaging system according to the present embodiment. The operation of the radiation imaging system will be described with reference to FIGS. Also in this embodiment, the reset scanning control unit 105 of the drive control unit 103 periodically performs reset scanning in order to prevent dark charges from accumulating in the two-dimensional sensor array constituting the radiation detection unit 2. The reset scanning control unit 105 selects a scanning line that is a target of reset scanning so as to sequentially reset and scan rows (scanning lines) that are not physically adjacent on the two-dimensional sensor array, and a conversion element of the selected scanning line is selected. Drive sequentially (TC1101, S1201).

  In step S1202, when the irradiation detection unit 101 does not detect the start of radiation irradiation (S1202-No), reset scanning is repeatedly executed (S1201). When the irradiation detection unit 101 detects the start of radiation irradiation (S1202-Yes), the reset scanning control unit 105 stops the reset scanning (TC1102, S1203). The readout scanning control unit 106 turns off all TFT switches on the two-dimensional sensor array and puts all the pixels on the two-dimensional sensor array into a charge accumulation state (TC1103, S1204). In the example of FIG. 11, the reset scanning is stopped in the middle of the reset scanning 1 in which the 2n-th row is reset-scanned. The drive control unit 103 stores, in the irradiation detection time information storage unit 104, the row number when the reset scanning is stopped, the type of partial reset scanning when the reset scanning is stopped, the output value information when the irradiation is detected, and the like. To do. The information stored here is used to read out radiation image data.

  In step S1205, the irradiation detection unit 101 determines whether or not radiation irradiation has ended. If the irradiation of radiation has not ended (S1205-No), the charge accumulation operation (TC1203, S1204) is continued.

  When the irradiation detection unit 101 detects the end of radiation irradiation (S1205-Yes), the readout scanning control unit 106 turns on all the TFT switches on the two-dimensional sensor array and sets all the pixels on the two-dimensional sensor array. To the charge output state. Then, in order to read out the electric charge accumulated by radiation irradiation, the readout scanning control unit 106 performs readout scanning control (TC1104a, 1104b) for sequentially scanning the rows on the two-dimensional sensor array, and the radiation image data obtained by radiography is obtained. Obtain (S1206).

  When performing a readout scan of a captured image, only a row (for example, the 2n + 1th row) other than a row (for example, the 2nth row) selected by the partial reset scan at the time of irradiation detection is selected, and the readout scan is performed first. carry out.

  For example, in the case of FIG. 10, the irradiation start is detected during the first partial reset scanning in which the 2 × n-th row is sequentially reset-scanned. At the time of readout scanning, partial readout scanning is performed in which radiation image data is sequentially read from the 2 × n + 1-th row, which is a row other than the 2n-th row (TC1104a, S1206a: first partial readout scanning).

  After the readout of the radiation image data from the 2 × n + 1th row is completed, partial readout scanning is performed to sequentially read out the radiation image data from the 2 × nth row (TC1104b, S1206b: second partial readout scanning). Here, in the radiation image data obtained by the first partial readout scanning (TC1104a, S1206a), there is no deterioration in the radiation image data at the time of irradiation detection. Therefore, after completion of the first partial readout scan (TC1104a, S1206a), the preview image generation unit 109 performs a preview image from the radiation image data obtained by the first partial readout scan by parallel processing with the second partial readout scan. Is generated (TC1105, S1207). Then, the communication control unit 114 transfers the preview image generated by the preview image generation unit 109 to the console 3 before the main image for diagnosis (TC1105, S1207).

  Since the preview image transferred to the console 3 has no image deterioration at the time of irradiation detection, the image correction processing for deterioration is not necessary, and can be immediately displayed on the display unit 4 (TC1106, S1208). As a result, the preview image can be transferred in advance without waiting for completion of reading of all the rows of the sensor array. Compared to the first embodiment, the delay time until the preview image display can be further reduced.

  After completing the reading operation of the radiation image data from the 2 × n-th row (TC1104b, S1206b), the reading scanning control unit 106 turns off the TFT switches of all the pixels on the two-dimensional sensor array to enter the charge accumulation state. (TC1107, S1209).

  In step S1210, the readout scanning control unit 106 determines whether the same time as the accumulation time (TC1103, S1204) at the time of radiation irradiation has elapsed (elapsed standby time). If the standby time has not elapsed (S1210-No), the charge accumulation operation is continued. Thereby, accumulation of dark charge is continued. If the readout scanning control unit 106 determines that the same time as the accumulation time at the time of radiation irradiation has elapsed (S1210-Yes), the readout scanning control unit 106 turns on all TFT switches on the two-dimensional sensor array and All the pixels on the sensor array are set in a charge output state. Then, the read scanning control unit 106 performs a read operation and acquires offset image data of only the dark charge component.

  At the time of readout scanning, the readout scanning control unit 106 sequentially reads offset image data from the 2 × n + 1th row, which is a row other than the 2nth row (TC1108a, S1211a).

  After the reading of the offset image data from the 2 × n + 1th row is completed, the read scanning control unit 106 sequentially reads the offset image data from the 2 × nth row (TC1108b, S1211b).

  The offset correction unit 110 performs offset correction using all the radiation image data stored in the captured image memory 112 and the acquired offset image data (S1212). The offset correction unit 110 acquires a captured image from which the dark charge component has been removed by offset correction that subtracts the component of the offset image data from the radiation image data. The communication control unit 114 transfers the captured image subjected to the offset correction by the offset correction unit 110 to the console 3 as a main image (TC1109, S1213).

  The drive control unit 103 reads information at the time of irradiation detection from the irradiation detection time information storage unit 104, and the communication control unit 114 transfers the information at the time of irradiation detection read by the drive control unit 103 to the console 3.

  The image processing unit 303 of the console 3 determines, from the information at the time of irradiation detection, the row number when the reset scanning is stopped, the type of partial reset scanning when it is stopped (non-adjacent row (scan line) selection method), Information on the output value when irradiation is detected is specified. The image processing unit 303 performs image correction that interpolates the loss of the captured image received using the specified information, and performs image processing suitable for various diagnoses (TC1110, S1214). The display unit 4 displays the captured image that has been subjected to image processing by the image processing unit 303 (TC1111, S1215: main image display).

  According to each of the embodiments described above, the preview image can be displayed without reducing the display delay of the preview image and without performing the process of correcting the image degradation at the time of radiation detection.

  Reset scanning when waiting for the start of radiation irradiation is sequentially performed on non-adjacent rows on the two-dimensional sensor array. A defect occurs only in the image data of the row that has been partially reset scanned at the start of radiation irradiation, and no defect occurs in the image data of the row that is not selected in the reset scan at the start of irradiation.

  By using this, a preview image is generated using only image data obtained from a line where no defect has occurred, and transferred to the display unit, so that the preview image is not corrected for image degradation. A preview image can be displayed. Thereby, a delay time (display delay) until the display of the preview image can be reduced, and a preview image that does not include the influence of pixel value loss can be displayed.

(Third embodiment)
Next, a radiation imaging apparatus according to the third embodiment will be described. The radiation imaging apparatus has a radiation detection array including a radiation detection array in which a plurality of conversion elements that convert radiation into electric charges are two-dimensionally arranged, and a plurality of scanning lines for selecting the conversion elements.

  The reset scanning control unit performs reset scanning control that performs reset scanning for discharging charges accumulated in the conversion elements corresponding to the scanning lines by sequentially selecting scanning lines that are not adjacent to each other. The irradiation detection unit detects the start of radiation irradiation during reset scanning. The readout control unit stops reset scanning in response to detection of the start of irradiation by the irradiation detection unit, reads out charges accumulated in the conversion element by radiation irradiation, and acquires image data based on the charges. A preview image generation unit 109 (generation unit) generates a preview image based on image data corresponding to a scan line for which reset scanning is not performed during radiation irradiation. The communication control unit (output unit) outputs the preview image generated by the preview image generation unit (generation unit) to an external device.

  The preview image generation unit excludes image data from image data read by the read control unit, excluding image data corresponding to a scan line on which reset scanning was performed between the start of radiation irradiation and detection of radiation irradiation. A preview image is generated based on the above.

  The reset scanning control unit and the readout control unit divide the plurality of scanning lines into a plurality of scanning line groups that are not adjacent to each other, and after scanning one line group of the plurality of scanning line groups, Perform a scan.

  The read controller reads in advance the charges accumulated in the conversion elements of the scan lines other than the scan line group in which the reset scan was performed when the radiation irradiation was detected. The preview image generation unit (generation unit) generates a preview image based on image data corresponding to the electric charges accumulated in the conversion elements of the scanning lines read out in advance.

  The plurality of scanning line groups include a first line group including even-numbered scanning lines as a radiation detection array and a second line group including odd-numbered scanning lines. Including. The communication control unit (output unit) includes, for example, a wireless communication circuit that wirelessly transmits the preview image generated by the preview image generation unit (generation unit). Note that transmission of the preview image is not limited to wireless communication, and wired communication using a cable may be used.

(Fourth embodiment)
The fourth embodiment will be described with reference to FIG. The driving method is different from that of the above-described embodiment, and the control subject of driving and the target to be driven are the same as those of the above-described embodiment, and thus description thereof is omitted. In this embodiment, after entering the accumulation operation (TC1303), the radiation image reading operation is performed from the row next to the row that was scanned immediately before the accumulation operation. In the example illustrated in FIG. 13, after the L8 row is reset and scanned, the radiation image reading operation is started from the L9 row, and 2n + 1 row scanning and 2n row scanning are performed.

  In addition, since the difference in accumulation time for each line between 2n rows and 2n + 1 rows can be reduced as compared with the example of FIG. 11, an image with less noise can be obtained.

  After that, when the 2n + 1 line is scanned to the end, the process returns to the beginning, and the remaining 2n + 1 line is scanned (until -1 of the stop line). L9, L11... Are scanned, and then L1, L3, L5, and L7 are scanned. Thereby, 2n + 1 line scanning is completed. The image signal obtained by the 2n + 1 row scanning is transferred to an external device in the same manner as in the previous embodiment. Of course, if the last reset-scanned row before the accumulation operation is 2n + 1 rows (even-numbered rows), the radiation image reading operation is performed from 2n rows.

  After the accumulation operation (TC1307) after the radiation image readout operation is performed, the offset image readout operation is also performed in the same manner as the above-described radiation image readout operation. As a result, the accumulation time can be reduced between the radiographic image and the offset image, and the dark component of the radiographic image can be corrected appropriately.

  In addition, between the radiographic image reading operation and the accumulation operation (TC1307), it is assumed that the 2n + 1 row scan performed immediately before the accumulation operation and the scan to the middle of the 2n row scan in the reset scan (TC1301) are performed. The accumulation time of each row is closer to that of the radiation image.

  Further, between the radiation image reading operation and the accumulation operation (TC1307), reset scanning is performed with a reverse bias applied to the pixels, and reset scanning is performed with the same forward bias as that at the time of resetting. (Refresh operation) is performed. According to this, it is possible to recover a dynamic range that is lowered by X-ray detection, particularly in an MIS type sensor, and obtain a good offset image.

  Further, the reading may be started from the L11 row or the L13 row, for example, without starting the reading from the row next to the L8 row that was last reset scanned before the accumulation operation. It is not always necessary to start reading from the row next to the L8 row.

(Fifth embodiment)
The fifth embodiment will be described with reference to FIG. The driving method is different from that of the above-described embodiment, and the control subject of driving and the target to be driven are the same as those of the above-described embodiment, and thus description thereof is omitted. In this embodiment, a plurality of rows are scanned simultaneously in the reset scan. In the example shown in FIG. 14, the TFTs connected to the row selection lines of a total of four rows L0, L2, L4, and L6 are turned on simultaneously. When the drive circuit is configured by a shift register, the operations up to L0, L2, L4, and L6 are scanned in as short a time as possible, and scanning is performed so that L0, L2, L4, and L6 are simultaneously turned on. In this case, the scanning timing of each row is slightly deviated, but the current flowing in the bias line can be increased substantially in the same manner as in the case where they are simultaneously turned on, which contributes to improvement in detection sensitivity. Here, the detection sensitivity is defined, for example, by the time from when X-ray irradiation is actually started until it is detected. From another viewpoint, it is defined by the minimum value of the X-ray intensity that can be detected within a predetermined time. The intensity here is, for example, a dose per unit time.

  In this embodiment, in the radiation image reading operation, a standby time is provided between the 2n + 1 row scan and the 2n row scan, and the image signal obtained by the 2n + 1 row scan is transferred to the outside. The waiting time ends when the transfer of the image signal obtained by the 2n + 1 line operation is completed, that is, when it is determined whether an ACK signal from the transfer destination is received or a time-out time related to transfer elapses. To be controlled. In response to such determination, scanning of 2n rows is started. Information on the waiting time t_wait is stored in the memory.

  Thus, by not performing the radiation image reading operation and the image transfer at the same timing, communication noise superimposed on the read image signal can be reduced. Such driving is more effective when wirelessly transferring images. Further, by performing image transfer between the 2n + 1 row scan and the 2n row scan, it is possible to display the preview image more quickly while reducing the influence of communication noise.

  In addition, during the offset image reading operation, a waiting time is provided between the 2n + 1 row scan and the 2n row scan by t_wait stored in the memory. After 2n + 1 row scanning is completed, control is performed so that 2n row scanning is started after t_wait has elapsed.

  Note that the above-described embodiments may be combined as appropriate. For example, in another embodiment, even when the radiation image readout operation is started from the row next to the last reset-scanned row before the accumulation operation as shown in FIG. 13, the radiation image readout operation as shown in FIG. A standby time is set between the 2n + 1 row scan and the 2n row scan. Then, during transfer of an image signal obtained by 2n + 1 row scanning, reading such as amplification and AD conversion by an image signal amplifier obtained by scanning or scanning is prevented.

  In other embodiments, even when a plurality of rows are scanned simultaneously as shown in FIG. 14, the timing control is performed so that the radiation image reading operation and the transfer are performed in parallel. In addition, combinations are possible as appropriate.

(Other embodiments)
The present invention can also be realized by executing the following processing. That is, software (program) that realizes the functions of the above-described embodiments is supplied to a system or apparatus via a network or various storage media, and a computer (or CPU, MPU, etc.) of the system or apparatus reads the program. It is a process to be executed.

Claims (12)

A radiation detection array in which a plurality of pixels that are connected to the scanning line and detect radiation and accumulate charges are arranged two-dimensionally;
Reset control means for performing reset scanning for sequentially discharging charges accumulated in the pixels;
Irradiation detection means for detecting the start of irradiation of the radiation;
Imaging control means for controlling to obtain the image signal by stopping the reset scanning in response to detection of the start of irradiation of the radiation and reading out the electric charge accumulated in the pixels by the irradiation of the radiation;
Generating means for generating image data based on the image signal;
An output unit that outputs the image data to an external device,
A plurality of scan line groups consisting of non-adjacent scan lines are formed,
The reset control means sequentially selects scan lines forming one scan line group in one scan and scans a plurality of times so that scan lines included in all scan line groups are selected. Reset scan,
The generation means generates preview image data based on an image signal from a pixel connected to a scan line that forms a scan line group other than the scan line group including the scan line selected when the radiation is applied. Radiation imaging characterized by generating image data for main image including image data corrected and generated based on an image signal from a pixel connected to a scanning line that was selected when radiation was emitted apparatus. Said imaging control means, the reading of the previous SL electric load, of the scan lines to exit from the scan line to begin once the reset scan, during said one reset scanning, when the reset scan is stopped The radiation imaging apparatus according to claim 1, wherein the radiation imaging apparatus starts from a scanning line that has not yet been selected. Said generating means, when the total number of lines of the scanning lines and N, based on the image signal to the scanning lines read before Symbol conductive load is read into N / 2-th counted from the start to scan lines, wherein The radiation imaging apparatus according to claim 2, wherein preview image data is generated.   4. The radiation imaging apparatus according to claim 1, wherein the output unit outputs the image data for main image to an external apparatus after outputting the image data for preview. 5. The scan line group includes a scan line group consisting of even lines and a scan line group consisting of odd lines,
The generation unit generates the preview image data based on an image signal of an odd line when the line where the reset scan is stopped is an even line, and the line where the reset scan is stopped is an odd line. 2. The radiation imaging apparatus according to claim 1, wherein the preview image data is generated based on an image signal of even lines.   The reset control unit stops the reset scanning when the radiation irradiation starts, and the imaging control unit uses the information of the radiation detection array when the reset scanning is stopped to start the radiation irradiation. The radiation imaging apparatus according to claim 2, wherein an image signal of a scanning line for which the reset scanning is not performed at a time is acquired. Said imaging control means, after obtaining the image signal from the pixel connected to the scan line in which the reset scanning at the time of the start of irradiation of the radiation is not performed, the reset scanning at the time of the start of irradiation before Symbol radiation The radiation imaging apparatus according to claim 6, wherein an image signal is acquired from a pixel connected to a scanning line on which the scanning has been performed.   The information of the radiation detection array at the time of stopping the reset scanning includes information indicating a scanning line on which the reset scanning has been performed at the time of starting irradiation of radiation, and scanning that is not adjacent when performing the reset scanning. The radiation imaging apparatus according to claim 7, further comprising information for selecting a line.   9. The radiation imaging apparatus according to claim 1, wherein the generation unit generates reduced preview image data obtained by thinning out image data from the preview image data. A radiation imaging apparatus comprising a radiation detection array in which a plurality of pixels that are connected to a scanning line and detect radiation and accumulate electric charges are two-dimensionally arranged, and a plurality of scanning line groups including non-adjacent scanning lines are formed. A control method,
Performing a reset scan for sequentially discharging charges accumulated in the pixels;
Detecting the irradiation start of the radiation;
Stopping the reset scanning in response to detection of the irradiation start;
Reading out charges accumulated in the pixels by irradiation with the radiation to obtain image signals;
Generating image data based on the image signal;
Outputting the image data to an external device,
In the step of performing the reset scanning, the scanning lines forming one scanning line group are sequentially selected by one scanning, and scanning lines included in all the scanning line groups are selected by scanning a plurality of times. Reset scan so that
In the step of generating the image data, a preview is performed based on an image signal from a pixel connected to a scan line that forms a scan line group other than the scan line group including the scan line selected when the radiation is applied. Image data is generated, and main image image data including image data corrected based on an image signal from a pixel connected to a scanning line selected when radiation is applied is generated. A control method for a radiation imaging apparatus.   The program for making a computer perform the control method of the radiation imaging device of Claim 10. A radiation imaging apparatus according to claim 1;
An information processing apparatus that processes data transmitted from the radiation imaging apparatus, and a radiation imaging system comprising:
The information processing apparatus includes:
A radiation imaging system comprising display means for displaying the output image data.

Images